/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: FlowList.java,v 1.2.4.1 2005/09/01 15:21:43 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.Iterator;
import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
public final class FlowList {

  private Vector _elements;

  public FlowList() {
    _elements = null;
  }

  public FlowList(InstructionHandle bh) {
    _elements = new Vector();
    _elements.addElement(bh);
  }

  public FlowList(FlowList list) {
    _elements = list._elements;
  }

  public FlowList add(InstructionHandle bh) {
    if (_elements == null) {
      _elements = new Vector();
    }
    _elements.addElement(bh);
    return this;
  }

  public FlowList append(FlowList right) {
    if (_elements == null) {
      _elements = right._elements;
    } else {
      final Vector temp = right._elements;
      if (temp != null) {
        final int n = temp.size();
        for (int i = 0; i < n; i++) {
          _elements.addElement(temp.elementAt(i));
        }
      }
    }
    return this;
  }

  /**
   * Back patch a flow list. All instruction handles must be branch handles.
   */
  public void backPatch(InstructionHandle target) {
    if (_elements != null) {
      final int n = _elements.size();
      for (int i = 0; i < n; i++) {
        BranchHandle bh = (BranchHandle) _elements.elementAt(i);
        bh.setTarget(target);
      }
      _elements.clear();          // avoid backpatching more than once
    }
  }

  /**
   * Redirect the handles from oldList to newList. "This" flow list
   * is assumed to be relative to oldList.
   */
  public FlowList copyAndRedirect(InstructionList oldList,
      InstructionList newList) {
    final FlowList result = new FlowList();
    if (_elements == null) {
      return result;
    }

    final int n = _elements.size();
    final Iterator oldIter = oldList.iterator();
    final Iterator newIter = newList.iterator();

    while (oldIter.hasNext()) {
      final InstructionHandle oldIh = (InstructionHandle) oldIter.next();
      final InstructionHandle newIh = (InstructionHandle) newIter.next();

      for (int i = 0; i < n; i++) {
        if (_elements.elementAt(i) == oldIh) {
          result.add(newIh);
        }
      }
    }
    return result;
  }
}
